Generally, a fuel cell is an electric power generation system that directly converts chemical reaction energy between hydrogen or hydrogen contained in a hydrocarbon based material such as methanol, ethanol, or natural gas and oxygen into electrical energy. The fuel cell, which is a clean energy source capable of substituting for fossil energy, generates outputs in various ranges by a stack configuration in which unit cells are stacked, and is used as a small and mobile portable power supply due to energy density four to ten times greater than that of a small lithium battery.
In addition, the fuel cell may be classified into a phosphoric acid fuel cell, a molten carbonate fuel cell, a solid oxide fuel cell, a polymer electrolyte membrane fuel cell, an alkaline fuel cell, and the like, based on a type of used electrolyte. These fuel cells are operated by the same principle, but different types of fuels, different operating temperatures, different catalysts, different electrolytes, and the like, are used in these fuel cells. Meanwhile, according to the related art, impurities of fuel cell reaction gas such as hydrogen and air may be introduced into in a fuel cell system of a vehicle while the vehicle is driven. In particular, stack performance may deteriorate due to the impurities introduced into the fuel cell system.